Bacterial resistance to the synergistic antibiotics of the PA 114, streptogramin, and vernamycin complexes.

A mutant of Bacillus subtilis was isolated that was resistant to the growth inhibitory activity of the synergistic antibiotics of the PA 114, streptogramin, and vernamycin complexes. Escherichia coli is naturally resistant to the action of these antibiotics. In both cases, it was shown that resistance was due to an inability of the bacteria to transport the antibiotics into the cell.